Body, Paint & StylingRear wheel arch rust help please

I know this has been covered on here a few times before, I have read a few posts on the subject. But I hope you don't mind me asking for some specific advice. Below are some pictures of my rear arch rust. This is a car I only bought last week. Having had no experience of dealing with rusty cars I naively thought I could DIY repair this by grinding it back and using fibreglass filler shaped to the arch profile. However people are now telling me that to do a proper job I'll need to have the metal cut out and new metal welded in.

I don't know what to do. The car cost me £1400 and mechanically is in great shape. I'd really like to get the rust sorted but not if it will cost thousands.

I don't know what it means when someone says that metal has to be cut out and replaced. Are we talking a few square inches or the whole rear quarter panel? Can't strips of metal be obtained and tacked in place to fit the profile?

If I do make a DIY repair, what will this mean? How long will I have till the arch disintegrates on me?

If I do nothing, what then?

I've no experience dealing with this kind of thing, and its worrying me. It would be great to do a proper repair but I simply can't afford to do that. I don't feel that just leaving it to rot is the right solution either. I'm worried if I start trying to DIY I'll make it worse.

Would really appreciate some views, advice and options.

I read a post where someone had recommended a place called MSGT motors in Walsall, this is only just round the corner from where I work, but their website just looks like a used car place. I'd be keen on taking it to a decent bodyshop to let an expert have a proper look and to get some prices and options.

You need to quite brave to tackle rust like that, as you need to sand back to bare metal, maybe even cut some holes out to get rid of rust spot all together. You then need to use some rust inhibitor, before applying some fibreglass, filler, several layers of primer, several layers of paint and them some top coat.

Thanks, I have watched that video before. It all looks very easy, but what I am most worried about is when I start my DIY repair the arch starts to just disintegrate underneath me. Filling holes I can deal with, but reconstructing the arch if large sections break up??

The reason they rust is from the original poor sealing between the inner and outer skin, it allowed moisture in and eventually the material goes porous, hence the bubbles appear under the paint and eventually the paint comes off.

Secondly they spot welded the inner to the outer and didnt seal up the gap caused by the welding.

The best way to repair would be a full 1/4 panel, but a smaller repair of the arch is more than adequate and any competent bodyshop could do it.

My suggestion is to refrain from spot welding the inner and outer skins though, instead shoosing to bond them together instead, not only is it stronger but it will protect and prevent further moisture and dirt ingress in the future.

... but a smaller repair of the arch is more than adequate and any competent bodyshop could do it.

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Can you give more detail on what exactly is done in this situation? I feel that I need to understand the scope of work so that when I go into a bodyshop I know what I'm asking.

This seam that you talk about, where the moisture gets in. Where exactly is it? I ask because on my car, the arch is rusting where it folds under the wheel arch, as well as on the 'side' of the arch. Underneath this 'fold under' (sorry I don't know how else to refer to it), there appears to be more metal. Can I not just bond fibreglass to this?

Personally I'd leave it, be mega money to get that sorted properly at a decent body shop plus getting the paint blended in so it matches. A poor repair of it and rust and bubbles will soon reappear!

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People have said this to me. But im still really unclear on what it is a bodyshop will/ could do. Nobody seems to be answering the question. What does it mean to cut out the metal and where do they get the replacement metal from?

If i leave it, then what happens to it over the next 6 months, year, 3 years? Its already unsightly with blistered paint. won't i at least buy myself time with a diy repair?

They will buy a wheel arch for it and cut the old panel off the car weld the new wheel arch in then use filler but it's the state of the inner panel that will be the problem. I'm sure there is a post on here of @Ichiban tourer getting the rear arches replaced there are loads of pictures of what they had to do. It will only get worse there is no real stopping of rust once it's started unless you get the panels cut out and replaced!

Well, since your car is worth £1500, goto a local body shop and ask them to estimate. If you try and be smart with them they will give you a dose of your medicine and be double smart and say it requires ££££ of repairs. Ask them nicely to atleast treat it for near future.. they might cut a few bits and pieces off and weld new ones and even if they don't replace the whole lot, I am sure the repair will last atleast a year or so. this way, you will have enough time to look at your options and not make the same mistake of buying a car with so much visible rust.

If I were in your situation I'd just bodge it e.g. open it up somewhere in the arch then spray in waxoyl, then use filler on the holes as and when they appear. IMO you'd get 3 years of life out of it that way before it becomes an MOT fail.

@chris2982 mate you had similar repair on you FR-V can you comment on how you tackled the repair.

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I ended up taking to a body shop for the work to be done..
i was very lucky though as none of the rust was on the face of the pannel.. caught it earlyenough so the only part affected was the folded edge.

I think I'd really like to get some rust treatment into the inside of the wheel arch in the short term. How do I get this inside? Can I access from under the arch lining?

This seam weld that people have mentioned, which joins the inner arch with the outer panel. If it is a continuous seam weld, then how does water get in? How does water get past the arch lining? If its spot welded, then that leaves holes, can I spray the rust treatment inside these same holes?

Hi again guys. I have attempted to draw a picture of how I think the arch area cross section looks, to try and understand where it is I need to get the rust treatment into.

Right so, I have drawn the inner arch above the wheel and the outer panel. Somewhere around the fold under, the inner arch and outer panel must come together. Is this where the gunk is collecting to cause the rust? I have drawn in brown the area where the rust is on the exterior.

So if I can get the rust treatment into this thin area between the inner arch and outer panel, that would be the right place?

Whereabouts is this seam weld? What I don't understand is, if its welded, where is the water/gunk getting in to that area in the first place?